The long-term objective of this project study is to develop a monoclonal antibody that inhibits the progression of diabetic retinopathy. Insulin-like growth factor-I (IGF-I) has been implicated in both endothelial dysfunction as well as the proliferative phase of the disease but IGF-I concentrations in retina are not increased. During hyperglycemia IGF-I activates both the PI-3 and MAP kinase pathways in endothelial cells by an aberrant mechanism that requires tyrosine phosphorylation of the transmembrane protein, SHPS-1 and this leads to enhanced cellular sensitivity to IGF-I. For SHPS-1 to be phosphorylated its extracellular domain must bind to another membrane protein, integrin associated protein (IAP). Under normoglycemic conditions the region of IAP that binds to SHPS-1 is cleaved but during hyperglycemia cleavage is inhibited. The antibody being developed disrupts IAP/SHPS-1 association thereby inhibiting this aberrant signaling pathway. Our phase1 studies showed that the antibody inhibited retinal capillary leakage, formation of acellular capillaries and pericyte ghosts. Therefore it appears that IAP/SHPS-1 association is required for retinopathy progression. The studies in aim 1 will determine if disrupting IAP/SHPS-1 results in inhibition of neovascularization. A polyclonal antibody directed against amino acids 71-80 in rat IAP will be injected into vitreous of hypoxemic rats and its effects on retinal neovascularization determined. These studies will also determine if the antibody can arrest the progression of established changes in capillary leakage and retinal thickening in that have occurred in diabetic rats. The studies in aim 2 will pursue the most important objective, humanization of the mouse monoclonal antibody that was prepared during phase 1. Murine amino acids that could potentially cause immunogenicity will be substituted with human residues in order to prevent autoimmunization. The humanized form will be tested to confirm that immunogenicity is been eliminated and that its affinity has not been reduced. The cDNAs encoding the antibody will be transfected into CHO cells and a high producing cell line developed. The purified protein will be tested to determine if it inhibits IGF-I stimulated signaling and changes in endothelial tube formation and permeabili- ty. If its efficacy is retained it will be administered intraocularly to monkeys to determine the effective concentration in vitreous that inhibits retinal endothelial dysfunction. These studies should definitively test the hypothesis that inhibiting IGF-I actions by inhibiting SHPS-1/IAP association in retina cells will inhibit the pathophysiologic changes that occur in diabetic retinopathy. Their successful completion will represent major progress toward the long term objective of this project; the development of an antibody that can be administered to patients with diabetic retinopathy that inhibits both the early events and prevents late stage manifestations of this disease. Since diabetic retinopathy is the leading cause of blindness in working age adults, there is a need for new therapies that are directed toward treatment of this complication.